The gas generator is for example used for inflating a safety bag (an airbag) in a motor vehicle in order to protect a person.
The type of gas generator concerned by the invention includes an outer wall delimiting at least partly at least one first chamber source of at least one gas and at least one second chamber for diffusing the gas outwards between which is found at least one nozzle including at least one first through-hole for letting the gas pass from the first chamber to the second chamber, the first hole of the nozzle being closed by at least one cap capable of being opened from the triggering of an electro-pyrotechnic device located towards the first chamber, the second diffusion chamber including in the wall at least one second hole for letting the gas pass outwards.
Presently, on the market, gas generators are found, the structure of which in majority consists of steel.
The majority steel proportion leads to a significant mass of the gas generators.
The fact that the outer wall is in metal has advantages for resistance to the internal pressure of the first chamber as well as during the letting through of the gas from the first chamber to the second diffusion chamber through the nozzle.
Indeed, this passage of gas in the nozzle should be accomplished in a very short time, of the order of a few tens of milliseconds or less for meeting the rapidity requirements for inflating an airbag in the field of automotive safety.
Thus, the first hole is subject to high gas flow velocities (Mach number greater than 1) as well as to very high temperatures during the operating time (about 3,000 K for 50 milliseconds).